The rotor blades are the primary elements of wind turbines for converting wind energy into electrical energy. The blades have the cross-sectional profile of an airfoil such that, during operation, air flows over the blade and produces a pressure difference between the sides. Consequently, a lift force, which is directed from a pressure side towards a suction side, acts on the blade. The lift force generates torque on the main rotor shaft, which is geared to a generator for producing electricity.
The wind turbine rotor blades are generally hollow structures, typically constructed by joining two halves, namely an upper (suction side) shell member and a lower (pressure side) shell member. The shell members are typically bonded together at bond lines along trailing and leading edges of the blade with a suitable bonding material. Any manner of internal support structure, such as one or more spar caps, a shear web, and the like, are also typically bonded to each of the shell members.
A current problem exists in that the shell members may separate along one or both of the edges due to any one or combination of physical variations in the bonding material, including: low bondage strength, manufacturing or application defect, excessive vibrations, cracks in the blade, leading edge erosion, and so forth. Such separation, if not detected early, can lead to complete blade failure, which can be very timely and costly to repair. Monitoring the blade at various locations for the onset of separations and taking necessary preventative measures can avoid this problem.
Accordingly, the industry would benefit from a wind turbine rotor blade edge monitoring system capable of early detection blade separation along one or both edges of the blade.